I know little about DSM but just a thought -the plants have been in a few days and still adapting to conditions but already having a extended lighting photoperiod.Should it maybe be low light for less hours and when growth and settlement is obvious increase.Take foot off lighting accellerator?
Of course its all about the quality of the young plant how well it i takes the transplant shock. But if you place a bunch under the same light all in the same pot (tank) youll have to turn your attention to the ones doing best. And take the worst ones out before you fill up if necessary. Because of this transplant shock almost every plant goes through more or less, it is best to take a moderate fertilized substrate, even better a inert substrate and start adding ferts after a few days rest. Because the first few days the plant wont do much. But it needs light to grow and as long its young and you like it to grow fast the longer the light periode the better and it doesnt need to be intense. Because it is still young and has tiny leaves and a not yet established root system. Than a lot of intense light mostly goes together with a high temperature, this will rather suck the plantlet dry than do any good. So moderate light and a nice accebtable temperature like not higher than 25C lights on and best not lower than 15C lights off, than you can easily go for an 18 hour periode. This will only benefit the plant to grow faster, after all that's what it does, grow under light. So give it more light it will want to grow more.
young plantlets are prone to grow weak and leggy when the period is (to) short.. Especialy seedlings will do that, that leggy so they will fall over.. There is a term for it but i do not know what it is called in english.
Its the same what submersed growth does when llight is not strong or periode not long enough the plant will tend to grow faster and leggy towards the light source (up)
In nature tropical plants get all day all the light there is, almost all year 12 hours.. The reason why we generaly cant give the plants 12 hours of light when submersed has nothing to do with the growth of the plants.. It has to do with the growth of something else we don't like.
A simple example, a Tomato is a tropical south american plant.. The farmers here can grow bigger tomatos than the natural plant in south america.. Why because we have longer light periode in the summer time. The plant can grow longer and bigger before it starts to flower and cary fruit. Geneticaly this plant strarts to flower when the days become shorter at around 12 hours daylight and less. Thats what they do with tomatos under artificial light, grow them larger under a longer periode than 12 hours, like 18 hours.. If the plant is large enough they go back to a constant 12 hour periode and bang lots of big tomatos, bigger than nature can provide..
in nature in the tropics in the wild the plant flowers in a much younger stage of its life..
